Season chicken with salt and pepper. Heat 1 tablespoon olive oil in 12-inch nonstick skillet over medium-high heat and cook chicken, stirring occasionally, until chicken is thoroughly cooked, about 5 minutes. Remove chicken and set aside.
Heat remaining 1 tablespoon olive oil and cook onion, stirring occasionally, until golden, about 4 minutes. Add wine and bring to a boil. Stir in broth and Knorr® Red Bell Pepper Pesto sauce mix and bring to a boil, stirring frequently. Reduce heat and simmer, stirring occasionally, 2 minutes. Stir in half and half and red pepper flakes. Return chicken to skillet and simmer until chicken is heated through, about 1 minute.
To serve, toss sauce with hot cooked fettuccine. Garnish with chopped walnuts, toasted pignoli nuts or chopped fresh basil. Bellisimo!